2,042 research outputs found
Reconciling Versioning and Context in Hypermedia Structure Servers
No full textContextual structure servers and versioning servers share a similar goal in allowing different views on a stored structure according to the viewer’s perspective. In this paper we argue that a generic contextual model can be used to facilitate versioning. In order to prove our hypothesis we have drawn on our experiences with OHP-Version to extend FOHM’s contextual model
Landmine Internal Structure Detection from Ground Penetrating Radar Images
No full textReliable landmine detection is still an unresolved problem. Demining operations are complex activities because of the large variety of existing landmine types, many different possible soil and terrain conditions, and environmental circumstances. Due to its ability of detecting both metallic and non-metallic objects, ground penetrating radar (GPR) is a promising method for detecting landmines that may allow faster and safer operations. As the performance of GPR is mainly governed by the target signature, the potential of discriminating target based on the presence of internal reflections could be a valuable advantage for identification and recognition process. This study demonstrates that from a set of high resolution GPR slices the internal design of the landmine can be properly imaged and characterised, confirming the applicability of the methodology and the validity of such an approach
Sparse Ground Penetrating Radar Acquisition: Implication for Buried Landmine Localization and Reconstruction
No full textThe effectiveness of the ground penetrating radar (GPR) imaging process and its capability of correctly reconstructing buried objects is strictly bounded to a correct acquisition strategy, both in terms of data density and regularity. In some GPR applications, such as landmine detection, these requirements may not be fulfiled due to logistical limitations and environmental obstacles. In the light of autonomous platform, possibly driven by a positioning device, the knowledge of the maximum affordable grid irregularity is essential. This experimental work, employing a data set acquired at a landmine test site, provides a demonstration that the same information content could be maintained even with a sparser data grid, compared to the commonly adopted requirements, mitigating the pressing demand for a precise samples positioning
Influence of internal structure on landmine radar signatures
No full textCheap and easy to use, landmines are among the favourite weapons in civil wars and wars of insurgency and are used by governments and guerrillas alike. These 'eternal sentinels' stand guard long after the conflicts have ended and kill and maim without mercy or discrimination. Therefore, there is a pressing need to remove these devices and to clear the contaminated land. As many landmines have low metal content they are difficult to detect using traditional techniques such as metal detectors, hence Ground Penetrating Radar (GPR) is an attractive tool in landmine clearance. Many investigations of landmine detection using GPR make use of surrogate landmine targets, since real landmines are difficult to obtain. This paper investigates the importance of the fidelity of such surrogates in terms of their external design, internal structure and explosive content
The Influence of Spatial Sampling in GPR Surveys for the Detection of Landmines and IEDs
No full textLandmine detection with GPR, is conditioned by a
properly focusing of the detected anomaly in the subsurface, and
this is theoretically possible only if the data have been acquired
fulfilling the spatial Nyquist criterion. An under-sampled data
will suffer from missing features, thus will carry a lower
informative level. Especially in extreme and adverse
environments, this constraint could be a huge issue. In addition,
target complexity or soil heterogeneity could introduce the need
for 3D acquisitions, thus significantly enhancing the time spent
by an operator on the field. The aim of this paper is to provide a
comparison between images obtained relaxing the Nyquist
criterion, to show that even if it does not hold, the informative
content of the final radar image will not be too much corrupted
Multi-perspective high range resolution profiles of landmines
No full textLandmine clearance is a severe and unresolved humanitarian issue. The development of low-cost, smaller, faster and lighter Ground Penetrating Radars (GPR), which can be mounted on unmanned platforms, will allow faster and safer 24/7 operations. This technology will make it possible to survey affected areas with more flexible trajectories and these will provide measurements of landmine signatures from many different aspect angles. As a result, multi-perspective information over wide angular windows and the behaviour of the signature as a function of the angle of illumination can be exploited. Landmine signatures are expected to present features that are less sensitive to the angle of illumination with respect to those of common cluttered objects, and this can lead to an improvement in detection and discrimination performance. In this paper, we present the results of an experimental trial carried out to collect the High Range Resolution Profiles (HRRPs) of two landmines, the SB-33 and the VS-50, off the ground. An analysis of the auto-correlation function of each range bin as a function of the aspect angle is presented together with that of the cross-correlation between profiles collected from different aspect angles
Quantum Griffiths Inequalities
No full textWe present a general framework of Griffiths inequalities for quantum systems. Our approach is based on operator inequalities associated with self-dual cones and provides a consistent viewpoint of the Griffiths inequality. As examples, we discuss the quantum Ising model, quantum rotor model, Bose-Hubbard model, and Hubbard model. We present a model-independent structure that governs the correlation inequalities
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Gaming addiction in adolescence (revisited)
No full textGaming addiction has become a topic of increasing research interest. Over the last 25 years, I have written many articles on adolescent video gaming for Education and Health as it is one of the research fields that is constantly evolving. In fact, over the last decade, there has been a significant increase in the number of scientific studies examining various aspects of online addiction particularly among adolescents and young adults (Kuss & Griffiths, 2012; Kuss, Griffiths, Karila & Billieux, 2014). Although the amount and the quality of research in the field has progressed much over this period, it is still in its infancy compared to other more established behavioural addictions (such as pathological gambling). This article briefly examines (i) how adolescent gaming addiction research has changed over the last three decades, (ii) how online gaming addiction has gained genuine psychiatric status, (iii) excessive gaming as an addiction, and (iv) where the gaming addiction field is going
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